Asymmetric synthesis of aryl‐substituted pyrrolidines by using CFAM ligand–AgOAc chiral system via 1,3‐dipolar cycloaddition reaction

Abstract

AbstractWe have prepared a ligand library based on a ferrocenyl aziridinyl methanol core unit (simply called FAM) having a phenyl group, a cyclohexyl group, and a naphthyl group to be used in 1,3‐dipolar cycloaddition (1,3‐DC) reactions for the synthesis of chiral pyrrolidines. These chiral ligands were used with AgOAc in 1,3‐DC reactions taking place between the aryl‐substituted azomethine ylides and N‐methylmaleimide as the dipolarophile. In each case, the expected aryl‐substituted pyrrolidines were obtained in good to excellent yields with acceptable enantioselectivities favoring only the endo product. The chiral catalyst system CFAM4–AgOAc was also used in 1,3‐DC reaction with different dipolarophiles such as dimethyl maleate, tert‐butyl acrylate, methyl acrylate, trans‐chalcone, and vinyl sulfone. In each case, the cycloadducts were obtained in acceptable yields albeit with low ee. Fortunately, it was possible to increase the ee up to >99% upon crystallization.